The present invention relates to an endodontic instrument adapted for use in performing root canal therapy on teeth.
Root canal therapy is a well-known procedure wherein the crown of the diseased tooth is opened so as to permit the canal to be cleaned and then filled. More particularly, a series of very delicate, flexible, finger held instruments or files are used to clean out and shape the root canal, and each file is manually rotated and reciprocated in the canal by the dentist. Files of increasingly larger diameter are used in sequence, to achieve the desired cleaning and shaping. When the canal is thus prepared, it is solidly filled with a filling material, which typically comprises a waxy, rubbery compound known as gutta percha. In one procedure, the gutta percha is positioned on an instrument called a compactor, and the coated compactor is inserted into the prepared canal and rotated and reciprocated to compact the gutta percha therein. The dentist thereafter fills the tooth above the gutta percha with a protective cement, and lastly, a crown may be fitted to the tooth.
A file of the described type is illustrated in U.S. Pat. No. 4,934,934, and a compactor of the described type is illustrated in U.S. Pat. No. 4,871,312. In each case, the instrument typically comprises a stainless steel shank having one or more helical flutes formed in the working portion of the shank.
A major problem associated with conventional endodontic instruments used in performing root canal therapy, is the fact that the instruments easily break while in the canal as a result of the rotating and reciprocating movement. More particularly, the instrument often engages and locks at a location adjacent the bottom end of the canal, such that continued rotation and reciprocation result in its breakage at a point adjacent the locking point. Upon breakage, a remnant of the instrument remains in the lower portion of the canal and it is difficult and often impossible to remove the remnant. If the remnant can not be removed, it is sometimes necessary to extract the tooth.
It is accordingly an object of the present invention to provide an endodontic instrument which is adapted for use in performing root canal therapy, and which is resistant to breakage during the procedure.
It is a more particular object of the present invention to provide an endodontic instrument of the described type, and which provides the dentist with a visual and/or tactile indication that it is about to break, thereby providing an opportunity to terminate the procedure before breakage, and so that a new instrument may be substituted for the weakened instrument.